1. Field of the Invention
The present invention relates to a gas sensor control apparatus and a gas sensor system for controlling a gas sensor element which detects a concentration of a specific gas.
2. Description of the Related Art
Conventionally, gas sensors are known which include a gas sensor element for detecting a concentration of a specific gas contained in exhaust emissions from an internal combustion engine, and a gas sensor control apparatus for controlling the gas sensor element. For example, Patent Literature 1 discloses a NOx sensor which includes a gas sensor element (a NOx sensor element) for detecting nitrogen oxides (NOx) as a specific gas, and a gas sensor control apparatus for controlling the gas sensor element so as to calculate a concentration of nitrogen oxides in a gas to be measured.
The NOx sensor element used for this purpose has a first measuring chamber and a second measuring chamber in an interior thereof, and includes a first pump cell and a second pump cell which are made of a solid electrolyte.
A gas to be measured is introduced into the first measuring chamber, and the first pump cell controls the gas contained in the first chamber gas to a predetermined oxygen concentration. The second chamber pump cell applies a predetermined second chamber pump voltage between a second chamber electrode which faces an interior of the second measuring chamber and a reference electrode which is exposed to an atmosphere of a reference oxygen concentration, to thereby dissociate an oxygen-containing specific gas contained in the second measuring chamber. In this manner, a current which corresponds to the concentration of the oxygen-containing specific gas in the second chamber gas flows between the second chamber electrode and the reference electrode. This enables the gas sensor control apparatus to detect a concentration of nitrogen oxides as a concentration of a specific gas based on the magnitude of the current.
[Patent Literature 1] JP-A-2009-168798